1. Field of the Invention
The invention relates to image display systems, and more particularly, to touch sensing circuits of image display systems.
2. Description of the Related Art
Recently, owing to emergence of information appliance (IA) products, touch panels have gradually replaced traditional human-machine interfaces, such as keyboards and mice. As users can operate the touch panel easily and conveniently, the application of touch panels has expanded to various fields, such as portable communication products and information products (e.g., PDA), banking/business systems, medical registry systems, factory-monitoring systems, public information-guide systems, and computer-based instruction systems. As for sensing methods, touch panels may be divided into capacitive types, sonic types, infrared types, resistive types, and magnetic induction types. Among the sensing method types, the capacitive types are applied to large-size touch panels. The contact of a finger or a pen point on a capacitive touch panel will create a capacitive change, which will further induce a current. Meanwhile, the X-coordinate and the Y-coordinate of the contact point can be calculated according to the induced current. Then, instructions or functions corresponding to the contract point may be transmitted.